Expandable tire building drum with alternating fixed and expandable segments, and contours for sidewall inserts

ABSTRACT

An expandable tire building drum, having alternating fixed ( 226, 326, 426 ) and expanding ( 228, 328, 428 ) segments (e.g.,  24  of each) in a center section ( 220, 320, 420 ) of the drum. The expanding segments are axially-extending and circumferentially spaced from one another, and are contoured (have recesses, or grooves) to accommodate tire components such as sidewall inserts. Two different mechanisms for expanding the center section are described. A first mechanism includes two wedge elements ( 358 ) which are axially moveable away from one another to expand the center section. Ramp elements ( 348 ) associated with the expanding segments ( 328 ) may thus be moved radially outward. Rubber bands ( 358 ) provide a restoring force for collapsing the center section. A second mechanism includes two guide rings ( 458 ) which are axially moveable towards one another for expanding the center section, and away from one another to collapse the center section. Overlapping links ( 462, 464 ) are provided between the guide rings and a support element ( 448 ) supporting the expanding segments ( 428 ).

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a Divisional application of U.S. application Ser. No.09/960,215, now U.S. Pat. No. 6,863,106, having a filing date of Sep.21, 2001 and a common assignee with present application.

This application relates to U.S. patent application Ser. No. 09/960,211entitled TIRE BUILDING DRUM HAVING EXPANDABLE CENTER SECTION ANDINDEPENDENTLY EXPANDABLE BEAD LOCK ASSEMBLIES IN THE END SECTIONS, filedon Sep. 21, 2001.

TECHNICAL FIELD OF THE INVENTION

The present invention relates to tire building drums for laying up tirecarcasses, more particularly to drums which are expandable between acollapsed position and an expanded position.

BACKGROUND OF THE INVENTION

It is known that in making vehicle tires, for example for automobiles,that manufacture of a so-called carcass is first achieved bysuccessively assembling several different components. In other words,the different carcass types included in a production range can bedistinguished from one another depending on the presence thereon of thevarious accessory components and/or the typology of the accessorycomponents themselves.

By way of example, when carcasses for tubeless tires are to be produced,that is tires that in use do not require the presence of an inner tube,the main components can be considered to include a so-called inner linerthat is a layer of elastomeric air-impervious material, a carcass ply, apair of annular metal elements, commonly referred to as bead cores,around which the opposite ends of the carcass ply are folded as well asa pair of sidewalls made of elastomeric material, extending over thecarcass ply at laterally opposite positions. The accessory componentsmay in turn comprise of one or more additional carcass plies, one ormore reinforcing bands for overlying the carcass ply or plies at theareas turned up around the bead cores (chafer strips), and others.

It is well known that the components of most pneumatic tireconstructions must be assembled in a way which promotes good tireuniformity in order to provide proper tire performance. For example, atread which “snakes” as it goes around the tire circumference will causewobbling as the tire is operated. For example, a carcass ply which islopsided (longer cords on one side of the tire than the other side) cancause a variety of tire nonuniformity problems including staticimbalance and radial force variations. For example, a tire which is notmeridionally symmetric (e.g., tread not centered between beads) cancause a variety of tire nonuniformity problems including coupleimbalance, lateral force variations, and conicity. Therefore, in orderto meet typical tire performance requirements, the tire industrygenerally expends considerable effort in producing tires with gooduniformity. Tire uniformity is generally considered to mean tiredimensions and mass distributions which are uniform and symmetricradially, laterally, circumferentially, and meridionally, therebyproducing acceptable results for measurements of tire uniformityincluding static and dynamic balance, and also including radial forcevariation, lateral force variation, and tangential force variation asmeasured on tire uniformity machines which run the tire under load on aroad wheel.

Although certain degrees of tire nonuniformity can be corrected inpost-assembly manufacturing (e.g., by grinding), and/or in use (e.g.,applying balance weights to the rim of a tire/wheel assembly), it ispreferable (and generally more efficient) to build-in tire uniformity asmuch as possible. Typical tire building machines comprise a tirebuilding drum around which the tire components are wrapped in successivelayers including, for example, an innerliner, one or more carcass plies,optional sidewall stiffeners and bead area inserts (e.g., apex),sidewalls and bead wire rings (beads). After this layering, the carcassply ends are wrapped around the beads, the tires are blown up into atoroidal shape, and the tread/belt package is applied.

Commonly-owned U.S. Pat. No. 5,591,288 (hereinafter referred to as“Becker”) discloses mechanical tire building drums for building extendedmobility pneumatic tires, and more specifically to a tire building drumhaving contours or depressions in its surface to facilitate buildingcertain tire designs. Attention is also directed to correspondingpublished European Patent Application No. 0 634 266 A2.

As noted by Becker, tire performance can be affected by addingcomponents to the tire or by adjusting the location of tire componentsin the tire during the tire building process. During the tire buildingprocess, it is important that components fit together well with aminimum of wrinkling of the tire components or trapping of air betweenthe components. If air is trapped between the uncured tire components,the tire may be defective and may have to be scrapped. During the tirebuilding process, if it appears the air has been trapped between tirecomponents, the tire builder must stitch the interfaces between theuncured elastomeric components to work any bubbles or trapped air frombetween the components. This stitching involves rolling a roller wheelalong the components, forcing the air to an edge of a component where itcan escape. The stitching process is time consuming and requires theskill of the tire builder.

As further noted by Becker, this problem is further magnified in tiredesigns where components are rather thick compared to other components.For example, when a component having a relatively square cross-section,such as a tire bead, is positioned adjacent a more planar component,such as a ply, the air may be trapped where the different-shapedcomponents interface. In tire designs where different-shaped componentsare necessarily placed next to each other, the problem of trapped air iseven more difficult.

As further noted by Becker, in one particular extended mobility tiredesign, inserts are positioned in the sidewall between the carcass pliesto enable the tire to support the weight of the vehicle even if the tireshould lose inflation pressure. These inserts are typically thicker thanthe plies which lie adjacent to them and it is important that this tirebe built without trapping air between the plies and inserts. Inaccordance with the present invention, an inventive tire building methodand drum have been designed which have features to accommodate thespecial production needs of such tires. These special features will bedescribed hereinafter and contribute to the building of a quality tirewithout trapping air.

Becker therefore provides a method of building a tire comprising thesteps of forming a liner into a cylinder, positioning first inserts toindent the liner cylindrical surface circumferentially at axially spacedinsert locations along the axis of the cylinder, laying a first ply ofreinforcing material around the cylindrical surface of the liner andfirst insert, positioning second inserts over the first ply at thespaced insert locations, laying a second ply of reinforcing materialover the first ply and the second inserts, positioning circular beads ateach end of the cylinder, expanding the first ply and the second ply toincrease the diameter of the cylinder between the circular beads toprovide shoulders at each end of the cylinder, turning edges of thefirst ply around the second ply over each of the beads, and positioninga belt and tread assembly around the second ply to form a precured tire.

Becker further provides a method of assembling tire components on a tirebuilding drum having a cylindrical surface comprising the steps oflaying a liner on the surface of the drum, positioning first insertsbelow the cylindrical surface and around a drum at insert locationsspaced from each end of the drum, laying a first ply of reinforcingmaterial around the drum over the cylindrical surface of the liner andfirst insert, positioning second inserts over the first ply at theinsert locations spaced from each end of the drum, laying a second plyof reinforcing material over the first ply and the second inserts,positioning circular beads at each end of the drum, expanding the drumto increase the diameter of the cylindrical surface and provideshoulders at each end of the drum, turning edges of the first ply andthe second ply over each of the beads, positioning a belt and treadassembly around the second ply, and contracting the drum for removal ofthe assembled tire components from the drum.

Becker further provides a tire building drum which has a cylindricalsurface, circular grooves in the surface at insert locations spaced fromeach end of the drum for positioning of first inserts below the surface,means for applying a first ply over the cylindrical surface, means forapplying second inserts over the first ply and the first inserts, meansfor applying a second ply over the first ply and second insert, meansfor expanding the drum providing shoulders at each end of the drum forapplying bead rings, means for turning up ends of the first ply aroundthe beads, means for applying a belt and tread assembly around thesecond ply and means for contracting the drum to remove the assembledtire from the drum.

Commonly-owned U.S. Pat. No. 4,855,008 discloses an expandable tirebuilding drum, especially a first stage solid pocket drum for building acarcass of a radial tire, having a segmental drum (10) with a pluralityof axially-extending, circumferentially spaced segments (36) withflexible connections (56) to shoulder pistons (32) at opposite ends ofeach segment (36). Wedge shaped bars (62) are positioned between thesegments (36) and are connected to center pistons (64) for urgingtapered side faces (80) of the bars into engagement with sloping sidefaces (78) of the segments (36). The shoulder pistons (32) and centerpistons (64) move radially outward to expand the drum. During the firststage operation, the tire reinforcing plies, beads and other componentsare assembled on the first stage drum and then the carcass is moved toanother location where it is shaped and the belt and tread applied. Inthe first stage assembly of the tire carcass it is important that thetire components be applied to contracted and expanded drum surfaceswhich are concentric and of uniform diameter along the length of thedrum. Expandible drums of different constructions have been usedheretofore; however it has been difficult to maintain a concentric drumsurface and a uniform diameter along the length of the drum in both theexpanded and contracted condition of the drum. For example, the drumsurface may be concentric and uniform in the contracted condition but isdistorted during expansion to a larger diameter. As a result, thecomponents added to the carcass on the expanded drum are not preciselyassembled which may adversely affect the uniformity of the tire.

U.S. Pat. No. 5,264,068 discloses an expandable drum includingadjustable stops for setting drum circumference. Tapering structures,each having axial slidability, are provided, and in response to a slidemove of the tapering structure, drum segments are each radially expandedor retracted. As noted therein, the tapering structure (12) is of aninner recessed frustum and is mounted over the drum shaft (10)longitudinally or axially slidable with the aid of a key (16), andhoused in the drum (14). The drum (14) is circumferentially divided intoa plurality of drum segments (17), each being like a sector, and eachsegment (17) is interiorly supported by a drum segment supporter (18).

Commonly-owned U.S. Pat. No. 4,976,804 discloses an expandable,segmental tire building drum (1) having a plurality of circumferentiallyspaced drum segments (28) radially movable by a set of links (36)pivotally connected to a pair of axially movable hub assemblies (34)slidably mounted on a drum shaft (12). Each of the segments (28) has acylindrical center portion (30) and end portions (32) with recessesproviding pockets (68) for the tire bead portions. The links (36) arepositioned between the end portions (32) providing space for large beadportions in the pockets (68) and at the same time the segments (28) areretractable to a small diameter to facilitate placing of a tire band(64) over the drum (10).

Commonly-owned U.S. Pat. No. 4,929,298 discloses a tire building drumincluding an expandable segmental cylinder assembly and a vacuumChamber. The drum (10) has a plurality of axially-extending,circumferentially spaced segments (18). The ends of the drum are sealedto provide a vacuum chamber (76) inside the drum which is incommunication with vacuum holes (78) in a cover sleeve (48) to hold tirecomponents on the drum surface (58) during assembly of the tirecomponents.

BRIEF SUMMARY OF THE INVENTION

According to the invention, an expandable tire building drum hasalternating fixed and expanding segments (e.g., 24 of each) in a centersection of the drum. The expanding segments are axially-extending andcircumferentially spaced-apart from one another, and their end portionsare contoured (have recesses, or grooves) to accommodate tire componentssuch as sidewall inserts. Two different mechanisms for expanding thecenter section are described.

A first mechanism includes two wedge elements which are axially moveableaway from one another to expand the center section. Ramp elementsassociated with the expanding segments may thus be moved radiallyoutward. Biasing elements provide a restoring force for collapsing thecenter section.

A second mechanism includes two guide rings which are axially moveabletowards one another for expanding the center section, and away from oneanother to collapse the center section. Overlapping links are providedbetween the guide rings and a base member supporting the expandingsegments.

Other objects, features and advantages of the invention will becomeapparent in light of the following description thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

Reference will be made in detail to preferred embodiments of theinvention, examples of which are illustrated in the accompanying drawingfigures. The figures are intended to be illustrative, not limiting.Although the invention is generally described in the context of thesepreferred embodiments, it should be understood that it is not intendedto limit the spirit and scope of the invention to these particularembodiments.

Certain elements in selected ones of the drawings may be illustratednot-to-scale, for illustrative clarity. The cross-sectional views, ifany, presented herein may be in the form of “slices”, or “near-sighted”cross-sectional views, omitting certain background lines which wouldotherwise be visible in a true cross-sectional view, for illustrativeclarity.

Elements of the figures are typically numbered as follows. The mostsignificant digit (hundreds) of the reference number corresponds to thefigure number. Elements of FIG. 1 are typically numbered in the range of100–199. Elements of FIG. 2 are typically numbered in the range of200–299. Similar elements throughout the drawings may be referred to bysimilar reference numerals. For example, the element 199 in a figure maybe similar, and possibly identical to the element 299 in another figure.Elements of the figures can be numbered such that similar (includingidentical) elements may be referred to with similar numbers in a singledrawing. For example, each of a plurality of elements collectivelyreferred to as 199 may be referred to individually as 199 a, 199 b, 199c, etc. Or, related but modified elements may have the same number butare distinguished by primes. For example, 109, 109′, and 109″ are threedifferent elements which are similar or related in some way, but havesignificant modifications, e.g., a tire 109 having a static imbalanceversus a different tire 109′ of the same design, but having a coupleimbalance. Such relationships, if any, between similar elements in thesame or different figures will become apparent throughout thespecification, including, if applicable, in the claims and abstract.Sometimes, similar elements are referred to with the suffixes -L and -R(e.g., 133L, 133R), which generally indicate left and right, as viewedin the drawing.

The structure, operation, and advantages of the present preferredembodiment of the invention will become further apparent uponconsideration of the following description taken in conjunction with theaccompanying drawings, wherein:

FIG. 1A is a schematic cross-sectional view of a tire building drum,with a tire carcass being laid up thereupon, according to the prior art;

FIG. 1B is a schematic cross-sectional view of a tire building drum,with a tire carcass being laid up thereupon, according to the prior art;

FIG. 2A is a perspective view of a tire building drum, according to thepresent invention;

FIG. 2B is a perspective view of a center section of the tire buildingdrum of FIG. 2A, in a collapsed position (condition), according to theinvention;

FIG. 2C is a cross-sectional view of the center section shown in FIG.2B, according to the invention;

FIG. 2D is a perspective view of a center section of the tire buildingdrum of FIG. 2A, in an expanded position (condition), according to theinvention;

FIG. 2E is a cross-sectional view of the center section shown in FIG.2D, according to the invention;

FIG. 2F is a perspective view of a typical expanding segment of thecenter section of the tire building drum of FIG. 2A, according to theinvention;

FIG. 3A is a perspective view of the center section of a tire buildingdrum, according to an embodiment of the invention;

FIG. 3B is a cross-sectional view of the center section of FIG. 3A, in afully-collapsed condition;

FIG. 3C is a cross-sectional view of the center section of FIG. 3A, in asemi-expanded (or semi-collapsed) condition;

FIG. 3D is a cross-sectional view of the center section of FIG. 3A, in afully-expanded condition;

FIG. 4A is a perspective view of the center section of a tire buildingdrum, according to an alternate embodiment of the invention, showing thecenter section in a fully-collapsed condition;

FIG. 4B is a perspective view of the center section of a tire buildingdrum, according to an alternate embodiment of the invention, showing thecenter section in a fully-expanded condition;

FIG. 4C is a schematic illustration of how the linkage mechanism of thealternate embodiment of FIG. 4A and FIG. 4B works, according to theinvention;

FIG. 4D is a plan view of an alternate embodiment of a component of thelinkage mechanism, according to the invention; and

FIG. 5 is a partial cross-sectional view of a tire carcass laid up on atire building drum, according to the invention.

DEFINITIONS

The following terms may be used throughout the descriptions presentedherein and should generally be given the following meaning unlesscontradicted or elaborated upon by other descriptions set forth herein.

“Apex” (also “Bead Apex”) refers to an elastomeric filler locatedradially above the bead core and between the plies and the turnup plies.

“Axial” and “axially” refers to directions that are on or are parallelto the tire's axis of rotation.

“Axial” refers to a direction parallel to the axis of rotation of thetire.

“Bead” refers to that part of the tire comprising an annularsubstantially inextensible tensile member, typically comprising a cableof steel filaments encased in rubber material.

“Belt structure” or “reinforcement belts” or “belt package” refers to atleast two annular layers or plies of parallel cords, woven or unwoven,underlying the tread, unanchored to the bead, and having both left andright cord angles in the range from 18 to 30 degrees relative to theequatorial plane of the tire.

“Breakers” or “tire breakers” refers to a belt or belt structure orreinforcement belts.

“Carcass” refers to the tire structure apart from the belt structure,tread, undertread over the plies and the sidewalls, but including thebeads, plies, and, in the case of EMT or runflat tires, the wedgeinserts sidewall reinforcements.

“Casing” refers to the carcass, belt structure, beads, sidewalls and allother components of the tire excepting the tread and undertread.

“Centerplane” refers to a plane intersecting a line which is normal tothe plane at a point which is midway between two other points on theline. The line may be an axis of a cylindrical member, such as a tirebuilding drum. A finished tire has a centerplane which is the“equatorial plane” of the fire.

“Chafer” refers to reinforcing material (rubber alone, or fabric andrubber) around the bead in the rim flange area to prevent chafing of thetire by the rim parts.

“Chipper” refers to a narrow band of fabric or steel cords located inthe bead area whose function is to reinforce the bead area and stabilizethe radially inwardmost part of the sidewall.

“Circumferential” refers to circular lines or directions extending alongthe perimeter of the surface of the annular tread perpendicular to theaxial direction, and can also refer to the direction of sets of adjacentcircular curves whose radii define the axial curvature of the tread, asviewed in cross section.

“Cord” refers to one of the reinforcement strands, including fibers ormetal or fabric, with which the plies and belts are reinforced.

“Crown” or “tire crown” refers to the tread, tread shoulders and theimmediately adjacent portions of the sidewalls.

“EMT tire” refers to Extended Mobility Technology and EMT tire refers toa tire which is a “runflat”, which refers to a tire that is designedprovide at least limited operational service under conditions when thetire has little to no inflation pressure.

“Equatorial plane” refers to a the plane perpendicular to the tire'saxis of rotation and passing through the center of its tread, or midwaybetween the tire's beads.

“Gauge” refers generally to a measurement, and often to a thicknessdimension.

“Inner liner” refers to the layer or layers of elastomer or othermaterial that form the inside surface of a tubeless tire and thatcontain the inflating gas or fluid within the tire. Halobutyl, which ishighly impermeable to air.

“Insert” refers to the crescent-shaped or wedge-shaped reinforcementtypically used to reinforce the sidewalls of runflat-type tires; it alsorefers to the elastomeric non-crescent-shaped insert that underlies thetread; it is also called a “wedge insert.”

“Lateral” refers to a direction parallel to the axial direction.

“Meridional profile” refers to a tire profile cut along a plane thatincludes the tire axis.

“Ply” refers to a cord-reinforced carcass reinforcing member (layer) ofrubber-coated radially deployed or otherwise parallel cords.

“Pneumatic tire” refers to a laminated mechanical device of generallytoroidal shape (usually an open-torus) having two beads, two sidewallsand a tread and made of rubber, chemicals, fabric and steel or othermaterials.

“Shoulder” refers to the upper portion of sidewall just below the treadedge.

“Sidewall” refers to that portion of a tire between the tread and thebead.

“Tire axis” refers to the tire's axis of rotation when the tire ismounted to a wheel rim and is rotating.

“Tread cap” refers to the tread and the underlying material into whichthe tread pattern is molded.

“Turn-up end” refers to a portion of a carcass ply that turns upward(i.e., radially outward) from the beads about which the ply is wrapped.

DETAILED DESCRIPTION OF THE INVENTION

Generally speaking, a conventional process for making a radial-plyautomobile tire includes an intermediate step of disposing two annularinextensible beads, each comprising a cable of steel filaments encasedin green rubber, over the other components of a green (“green” meaningas yet uncured and still tacky) tire carcass on a tire building drum. Anannular cross-sectionally triangular rubber filler called an “apex” maybe added. Portions of the ply components that extend beyond the beadsare then turned up around the beads, forming “turn-ups”. Then, the greencarcass is typically removed from the tire building drum and mounted ona “second stage machine” where it is inflated (reshaped) to a toroidalshape, and its radially-outer surface is pressed against a tread andbelt package. In subsequent steps, the green carcass is stitched (rolledwith a roller) to remove air pockets and adhere internal surfacestogether. The resulting assembly is inserted into a mold (vulcanizingpress) to cure under heat (typically 350 degrees Fahrenheit) andpressure to become a finished tire.

FIG. 1A corresponds generally to FIG. 9 of Becker, and illustrates(schematically, and in a greatly simplified manner) an exemplary tirebuilding drum 102 of the prior art. The drum 102 is generallycylindrical, having two ends 102 a and 102 b, an axis of rotation 104extending between the two ends, and a cylindrical outer surface 106. Acenterplane (CP) is indicated on the drawing, and is generally a planewhich bisects a carcass being laid up on the tire building drum.

In a typical (again, greatly simplified, for illustrative clarity) tirebuildup, an inner liner 108 is applied on the surface of the drum 102,and two tire sidewall insert components (“inserts”) 110 a and 110 b(collectively referred to as “110”) are disposed at longitudinally(axially) spaced apart positions on the inner liner 108, as shown. Next,a first ply 112 is disposed over the inner liner 108 and inserts 110.This results in a green tire carcass having a nominally cylindricalshape. However, as is evident from the illustration of FIG. 1A, theaddition of the sidewall inserts 110 between the inner liner 108 and theply 112 causes there to be two “bumps” (protrusions), which are regionsof increased outside diameter (“OD”), in the outer surface of thecarcass. As can be seen, these bumps protrude significantly upwardlyfrom the outer surface of the tire building drum and create significantprotrusions 18 in these areas. Subsequent tire components such as asecond carcass ply are difficult to force into such a nonplanar contour.At the locations of the protrusions, air can be trapped within the tire,leading to the aforementioned problems.

Next, two beads 114 a and 114 b (collectively “114”) are added to thetire carcass. Each bead 114 is a substantially inextensible circularhoop, having an inside diameter (“ID”) which is substantially equal toor preferably only slightly greater than the OD of the ply 112 (in areasother than where there are bumps). The beads 114 are shown as beingslightly axially outboard of the inserts 110, and are shown as having around (versus hexagonal) cross-section for sake of illustrative clarity.A second ply (not shown) may be added to the carcass, and the outer endportions of the carcass may be turned up. Finally the carcass may betransferred to another (second stage) machine for adding a treadpackage, etc.

FIG. 1B corresponds generally to FIGS. 2–7 of Becker, and illustrates analternate embodiment of an exemplary tire building drum 122 of the priorart. The drum 122 is generally cylindrical, having two ends 122 a and122 b, an axis of rotation 124, and a generally cylindrical outersurface 126. The drum 122 differs from the drum 102 of FIG. 1A primarilyby virtue of having annular recesses (pockets, grooves) 136 a and 136 b(collectively referred to as “136”) in its outer surface at longitudinal(axial) positions corresponding to the positions of and related to thedimensions of inserts 130 a and 130 b (collectively referred to as“130”) and extending about the circumference of the drum 122. In thisexample, the inner liner 128 is applied to the surface 126 of the drum122. Then the inserts 130 are applied, and fit (nestle) down into therecesses 136. Then a ply 132 is applied. This results in a green tirecarcass having a substantially cylindrical shape. In contrast to thetire carcass formed in FIG. 1A, the addition of the inserts 130 betweenthe inner liner 128 and the ply 132 does not cause there to be two“bumps” in the outer surface of the carcass. Since there aresubstantially no bumps, and the outer surface of the tire carcass beinglaid up is substantially cylindrical, having a substantially uniform OD,it is (among other things) possible to mount two beads 134 a and 134 b(collectively referred to as “134”) onto the carcass by sliding themboth on from one end (e.g., 122 a) of the drum 122.

FIGS. 2A through 2D illustrate, generally, the tire building drum 202 ofthe present invention. The drum 200 is generally cylindrical, having twoends 202 a and 202 b, an axis of rotation 204 extending between the twoends, and a cylindrical outer surface 206. The drum 202 has an overallaxial length “L” between the two ends. A spindle (or drum support shaft)extends along the axis 204 and has an end 208 a extending from the end202 a of the drum 202, and an end 208 b extending from the end 202 b ofthe drum 202.

The drum 202 has a center section 220 which is generally cylindrical,and centered about the axis 204. The center section 220 has a width(more properly, axial length) of L_(C). The drum 202 has a first endsection 222 which is coaxial with the center section 220, and which isdisposed axially at one end of the center section 220. The drum 202 hasa second end section 224 which is coaxial with the center section 220,and which is disposed axially at an opposite end of the center section220. The two end sections 222 and 224 are, for purposes of the presentinvention, substantially identical to (i.e., mirror images of) oneanother, each having an axial length of (L−L_(C))/2. The end sections222 and 224 are axially-outward of the center section 220. The drum,more significantly the center section 220 of the drum, has a centerplane(compare CP, FIG. 1A), which is a plane intersecting the axis 204 midwaybetween the ends of the center section (typically also midway betweenthe ends 202 a, 202 b) of the overall drum. The axis 204 is, bydefinition, normal to the centerplane.

The center section 220 is circumferentially segmented, having aplurality of elongate fixed segments 226 alternating with a likeplurality of elongate expanding segments 228. As best viewed in any ofFIGS. 2B–2D, there are suitably 24 (twenty four) fixed segments 226alternating with 24 (twenty four) expanding segments 228. The expandingsegments 228 are axially-extending and circumferentially spaced from oneanother, and end portions of each is contoured to have annular recesses(pockets, grooves) 236 a and 236 b (collectively referred to as “236”;compare 136) in its outer surface at longitudinal (axial) positionscorresponding to the positions of and related to the dimensions ofsidewall inserts (not shown, compare 130) which will be applied duringthe carcass layup process, described hereinabove. The pockets 236 canbest be viewed in FIG. 2F, wherein can also be viewed two turnup bladder(not shown) anchor points 238 a and 238 b in the outer surface of theexpanding segment. In FIGS. 2F and 5A, it is seen that end portions ofthe expanding segments 238, 538 are contoured to have pockets 236, 536for receiving components (e.g., sidewall inserts) of a tire carcassbeing laid up on the drum.

The fixed segments 226 are elongate, generally rectangular incross-section and have a length substantially equal to L_(C). The fixedsegments 226 typically have a fixed width or have a width proportionalto the number of total segments. The expanding segments 228 are alsoelongate, generally rectangular in cross section, and have a lengthsubstantially equal to L_(C).

It is within the scope of the invention that there are any suitablenumber of fixed and expanding segments, for example, rather than twentyfour of each, anywhere from eighteen to thirty of each. It is alsowithin the scope of the invention that the number of fixed segments isnot exactly equal to the number of expanding segments. It is also withinthe scope of the invention that the expanding segments do not all havethe exact same width. The same applies to the fixed segments. Selectedones of the fixed and/or expanding segments can be “special purpose”segments, such as for communicating vacuum to an inner liner being laidup on the drum.

The center section 220 is expandable, between a collapsed (or retracted,or contracted) condition, shown in FIGS. 2B and 2C and an expanded (orextended) condition (or “fully” expanded position), shown in FIGS. 2Dand 2E. Mechanisms for effecting expansion and collapse of the centersection 220 are described hereinbelow, and accommodate partiallyexpanding the center section to one (or more) “semi-expanded” positions.Generally, each of said expanding segments 228 is expandable from afirst radius in the a collapsed condition of said drum to a second,greater radius in an expanded condition of said drum.

“Dual Cone” Mechanism for Expanding/Collapsing the Center Section

FIGS. 3A–3D illustrate the major components of an expandable centersection 320 (compare 220) of a tire building drum, according to anembodiment of the invention. In the view of FIG. 3A, one of a plurality(e.g., 24) of expanding segments 328 (compare 228) is shown, and acorresponding one of a plurality (e.g., 24) of fixed segments 326(compare 226) is shown. In FIGS. 3B–3D, the expanding segment 328 isshown, but not the fixed segment 326, for illustrative clarity. Aspindle 308 is illustrated highly schematically in FIGS. 3B–3D, and isomitted from FIG. 3A, for illustrative clarity. A base member 346 forthe fixed segment 326 is shown in FIG. 3A only, for illustrativeclarity. A base (ramp) element 348 for the expanding segment 328 is bestviewed in FIGS. 3B–3D.

Two guide elements (flanges) 340 a and 340 b (collectively referred toas “340”) are disposed at axially spaced apart positions on a spindle308 (compare 208) which extends along the axis 304. The flanges 340 aresuitably in the form of generally planar discs which are centered on theaxis 304, and are parallel with one another. Each flange 340 has aninner surface which faces, and is parallel with the inner surface of theother flange 340. The flanges 340 are essentially fixed to the spindle308, which means that they will rotate with the spindle, and that theyare at a fixed axial distance apart from one another. The flanges 340are preferably centered about the centerplane. The flanges 340 are adistance apart which, as illustrated, is less than the length L_(C) ofthe segments 326, 328.

The inner surfaces of the flanges 340 a and 340 b are provided with aplurality of radially-extending grooves 342 a and 342 b, respectively. Agiven groove 342 a on the guide plate 340 a corresponds to, and is atthe same circumferential position on the spindle 308 as, a given groove342 b on the guide plate 340 b. These two given grooves 342 a, 342 bform a given pair of grooves and, for example, there are 24 (twentyfour) pairs of grooves, spaced at even intervals about the innersurfaces of the flanges 340. Each of these given pairs of grooves 342 a,342 b function as a track for guiding an expanding segment supportmember (ramp element) 348 associated with an expanding segment 328,radially inward and outward, as discussed hereinbelow.

Each expanding segment 328 has a ramp element 348 associated therewith.(For 24 expanding segments 328, there are 24 ramp elements 348.) Theramp element 348 is essentially a flat planar element having four edges(sides)—a top edge for supporting the expanding segment 328, a bottom“ramped” edge which functions as a ramp surface for being acted upon bytwo movable wedge elements 358 (described in greater detailhereinbelow), a first side edge which rides in the groove 342 a of agiven groove pair, and a second side edge which rides in the groove 342b of the given groove pair. Preferably, the ramp element 348 is separatefrom the expanding segment 328, but it is within the scope of theinvention that it is integrally formed therewith. In the case that theramp element 348 is not formed integrally with the expanding segment328, the expanding segment 328 may be attached in any suitable manner tothe ramp element 348.

The inner surfaces of the flanges 340 a and 340 b are also provided witha plurality of radially-extending grooves 343 a and 343 b, respectively.Each of the radially-extending grooves 343 a and 343 b are interspersedbetween the radially-extending grooves 342 a and 342 b Theradially-extending grooves 343 a and 343 b are shorter than theradially-extending grooves 342 a and 342 b. A given groove 343 a on theguide plate 340 a corresponds to, and is at the same circumferentialposition on the spindle 308 as, a given groove 343 b on the guide plate340 b. These two given grooves 343 a, 343 b form a given pair of groovesand, for example, there are 24 (twenty four) pairs of grooves, spaced ateven intervals about the inner surfaces of the flanges 340. Each ofthese given pairs of grooves 343 a, 343 b function as a track forreceiving and securing a fixed segment support member 346 associatedwith a fixed segment 326, as discussed hereinbelow. The base member 346is essentially a rectangular block, extending between grooves of theflanges and having four edges (sides)—a top edge for supporting thefixed segment 326, a first side edge which fits in a groove 343 a, asecond side edge which fits in a groove 343 b, and a generally flatbottom edge. In the case of 24 (twenty four) fixed segments 326, thereare 24 (twenty four) base members 346 extending between 24 pairs ofgrooves 343 a, 343 b. (The side edges of the base members are receivedin the grooves.) This accounts for the total overall number of groovesin each flange (and the total overall number of groove pairs in theflanges) being 48 (forty eight)—24 pairs of grooves for guiding theexpanding segments 328 as they move radially in and out, and 24 pairs ofgrooves for locating the fixed segments 326 between the expandingsegments 328 even though radial movement is not contemplated or required(to the contrary, the fixed segments are supposed to remain at selectedradial positions). Preferably, the base member 346 is separate from thefixed segment 326, but it is within the scope of the invention that itis integrally formed therewith. In the case that the base member 346 isnot formed integrally with the fixed segment 326, the fixed segment 326may be attached in any suitable manner to the base member 346.

In FIG. 3A, it can be seen that the fixed segment 326 has an axiallength which is substantially the same as the axial length of theexpanding segment 328, and that the axial length L_(C) of both isgreater than the spacing between the two flanges 340, and that they are“centered” with regard to the flanges 340 (and the centerplane).

Two biasing members 338 a and 338 b (collectively referred to as “338”)are provided. One of the biasing members, 338 b) is shown in phantom inFIG. 3A. The other of the biasing members, 338 a, is shown in phantom inFIGS. 3B–3D, for illustrative clarity. The biasing members 338 aredisposed at axially spaced apart positions about the spindle 308, andare suitably in the form of rubber bands extending through correspondingholes 343 a and 343 b in each of the ramp elements 348. These rubberbands 338 exert a “collapsing” radial force on the ramp elements 348 inthe direction of the axis 304. As shown in FIG. 3A, the base members 346for the fixed segments 326 may also be provided with holes 344 a and 344b, through which the rubber bands 338 extend.

Two tapered (wedge) elements 358 a and 358 b (collectively referred toas “358”) are disposed at axially spaced apart positions on the spindle308 (on either side of the centerplane). The wedge elements 358 aresuitably in the form of generally planar discs (rings, since they arediscs with a hole in the middle) which are centered on the axis 304, andare parallel with one another. The outer faces of the wedge elements 358are tapered. Therefore, the wedge elements 358 are frustroconical, andmay be referred to as “cones”, or “cone-shaped elements”, or “conicalelements”. The wedge elements 358 are not fixed to the spindle 308.Rather, although they may be keyed (or splined) to the spindle so thatthey will rotate with the spindle, they are free to move axially(traverse) along the spindle, towards and apart form one another, from aminimum distance (essentially touching one another), to a maximumdistance from one another, remaining parallel with each otherirrespective of the axial distance form one another.

In FIG. 3B, the center section 320 is shown in its collapsed (or“fully-collapsed”) position. In this position, the wedge elements 358are close together (e.g., essentially zero distance apart from oneanother, with their bases touching, or nearly touching), and the rampelement 348 and, consequently, the expanding segment 328 is at itsminimal radial distance from the axis 304. In other words, the diameterof the center section 320 is at a minimum in this collapsed (retracted)position. In this collapsed position, the outer surface of the centersection 320 has substantially the same diameter as that of the outersurfaces 306 (compare 206) of adjacent end sections 322 and 324 (compare222, 224). In this collapsed position, a tire component, such as theinner liner (e.g., 504, see below) of a tire carcass, may be applied.

In FIG. 3C, the center section 320 is shown in its semi-expandedposition. In this position, the wedge elements 358 are spread apart fromone another (but not as far apart as they are capable of spreading), andthe ramp element 348 and, consequently, the expanding segment 328 is ata greater radial distance from the axis 304. In other words, thediameter of the center section 320 is now larger, or expanded. In thissemi-expanded position, the outer surface of the center section 320 hasa slightly greater diameter than that of the outer surfaces 306 (compare206) of adjacent end sections 322 and 324 (compare 222, 224). In thissemi-expanded position, a tire component, such as the ply (e.g., 508,see below) of a tire carcass, may be applied.

In FIG. 3D, the center section 320 is shown in its fully-expandedposition. In this position, the wedge elements 358 are spread (havemoved) farther apart from one another (essentially as far apart as theyare capable of spreading, their bases far apart from one another), andthe ramp element 348 and, consequently, the expanding segment 328 is atan even greater radial distance from the axis 304. In other words, thediameter of the center section 320 is now even larger, or more expanded.In this fully-expanded position, the outer surface of the center section320 has a much greater diameter than that of the outer surfaces 306(compare 206) of adjacent end sections 322 and 324 (compare 222, 224).Concurrently with the drum in the fully-expanded position, separatelyactuated bead locks (not shown) cause the beads to be firmly set. Next,the ends of the carcass can then be turned up, in a final step ofcarcass construction. Then, the center section 320 of the drum can bepartially collapsed (e.g., returned to a semi-expanded position), thebead locks collapsed and the carcass can be removed for furtherprocessing, such as the application of a tread package in a second stagetire building machine.

The two wedge elements 358 are in the form of cones (more accurately,frustroconical), disposed coaxially (having the same axis) with theirbases opposing (facing) one another, and their apexes (albeit truncated)remote from one another. It is preferred that the two wedge elements 358remain at all times, throughout their range of axial movement,equidistant from the centerplane of the center section 320 of the drum.The bottom edge (inner surface) of the ramp element 348 is V-shaped,with two intersecting ramp surfaces, one for each of the wedge elements358. In this manner, forces exerted by the wedge elements 358 are evenlydistributed along the length of the ramp element 348 and, consequently,the expanding segment 328. The angle along the outer edges (faces) ofthe wedge elements 358, and the corresponding angle along the inneredges (surfaces) of the ramp elements 348 is suitably between 20 degreesand 45 degrees, such as approximately 30 degrees, more particularly suchas 33 degrees, with respect to the axis, or more parallel to the axisthan perpendicular thereto. This angle, of course, remains constantirrespective of the axial positions of the wedge elements 358. As thewedge elements 358 move farther apart from one another, the expandingsegments 328 are urged radially outward from the axis 304.

The expanding segment 328 has a length L_(C). The fixed segment 326 hasa length substantially equal to L_(C). The flanges 340 are spaced aparta distance less than the length L_(C). In the illustrations of FIGS.3A–3D, a total of 48 (forty eight) grooves 342 are shown in each flange340. As discussed hereinabove, 24 of these grooves on each flange form agiven pair of grooves for guiding the ramp elements 348 as they areforced radially outward and return radially inward. As best viewed inFIG. 3A, the base member 346 extends between intermediate pairs ofgrooves 342 in the flanges 340. Also, the base members 346 must passover (by, through) the wedge elements 358. Therefore, the wedge elements358 have 24 notches 356 at evenly spaced circumferential positions aboutthe outer surface of their respective bases for receiving a bottom edgeof the base member 346 as it passes by. This serves to ‘lock’ the wedgeelements 358 in fixed circumferential positional relationship withrespect to the flanges 340, while allowing the wedge elements 358 tomove axially back and forth in the space between the flange elements340.

It is therefore seen that expansion of the center section 320 of a tirebuilding drum can be accomplished using a traversing dual cone mechanismwhich exerts radial forces on the expanding segments 328 which aresymmetrical about the centerplane of the drum (i.e., of the centersection 320). With only one tapering structure, such as in U.S. Pat. No.5,264,068, such symmetry cannot be accomplished. Applying expandingforces, with symmetry about the centerplane, can be critical toachieving uniformity in the layup of a tire carcass.

Although not shown, any suitable mechanism can be used for moving thetapered wedge elements axially 358 outward to effect expansion of thecenter section 320, and axially inward (towards one another) forpermitting retraction of the center section 320.

Suitable dimensions for the center section 320 are:

-   -   diameter collapsed=400 mm    -   diameter semi-expanded=420 mm    -   diameter fully-expanded 476 mm (expansion of 76 mm)    -   minimum center section width (L_(C)) of 250 mm

When the center section 320 is collapsed, the surface of the drum issubstantially continuous, smooth, uninterrupted (flat), and this isadvantageous for innerliner application. It is within the scope of theinvention that means for providing a vacuum, through selected ones ofthe segments (either fixed or expanding), to the surface of the drum, tohold the innerliner securely thereon, be provided, in any suitablemanner. When the center section is semi-expanded, the surface is alsosubstantially flat, such as would be advantageous for ply application.

“Overlapping Linkage” Mechanism for Expanding/Collapsing the CenterSection

FIGS. 4A–4C illustrate an alternate embodiment of a mechanism forexpanding and collapsing the center section of a tire building drum.Whereas the embodiment of FIGS. 3A–3D used a dual cone and rampmechanism for expansion, and rubber bands for collapsing the centersection, in this embodiment the linkage is capable of both expanding andcontracting the expanding segments of the center section.

FIGS. 4A–4C illustrate the major components of an expandable centersection 420 (compare 320) of a tire building drum, according to analternate embodiment of the invention. In the illustration of FIG. 4C,one of a plurality (e.g., 24) of expanding segments 428 (compare 328) isshown. In the views of FIGS. 4A and 4B, the expanding segment isomitted, for illustrative clarity. It will be understood that thegeneral alternating arrangement of fixed and expanding segments issubstantially the same in this embodiment as in the previously-describedembodiment. In describing this embodiment, the fully-collapsed positionof the center section 420 is shown in FIG. 4A, and the fully-expandedposition of the center section 420 is shown in FIG. 4B. It will beunderstood that in this, as in the previous embodiment, the drum may beexpanded (or collapsed) to any position (diameter) betweenfully-collapsed and fully-expanded. A spindle (compare 308) extendsalong the axis 404 of the drum, but it omitted, for illustrativeclarity. Although not shown, the center section is provided with fixedsegments (e.g., 326), in the same (or similar) manner as was thepreviously-described embodiment.

Two flanges 440 a and 440 b (collectively referred to as “440”; compare340) are disposed at axially spaced apart positions on the spindle. Theflanges 440 are substantially similar to the flanges 340 of the previousembodiment, and are suitably in the form of generally planar discs whichare centered on the axis (304), and are parallel with one another. Eachguide element 440 has an inner surface which faces, and is parallel withthe inner surface of the other guide element 440. The flanges 440 areessentially fixed to the spindle (308), which means that they willrotate with the spindle (308), and that they are at a fixed axialdistance apart from one another.

The inner surfaces of the flanges 440 a and 440 b are provided with aplurality of radially-extending grooves 442 a and 442 b, and 443 a and443 b respectively. Again, this is comparable to the grooves 342 a and342 b, and 343 a and 343 b, respectively of the previously-describedembodiment. A given groove 442 a on the guide plate 440 a correspondsto, and is at the same circumferential position on the spindle as, agiven groove 442 b on the guide plate 440 b. These two given grooves 442a, 442 b form a pair of grooves and, for example, there are 24 pairs ofgrooves, spaced at even intervals about the inner surfaces of theflanges. Each pair of grooves functions as a track for guiding anexpanding segment support, or base (support) element 448 (compare 348)as it moves radially inward or outward from the axis, as discussedhereinbelow. Further, a given groove 443 a on the guide plate 440 acorresponds to, and is at the same circumferential position on thespindle as, a given groove 443 b on the guide plate 440 b. These twogiven grooves 443 a, 443 b form a pair of grooves and, for example,there are 24 pairs of grooves, spaced at even intervals about the innersurfaces of the flanges. Each pair of grooves functions as a track forsecuring base (support) element 446 (compare 346) which is secured tothe fixed segments, as discussed hereinbelow.

Each expanding segment 428 has a support element 448 associatedtherewith. (For 24 expanding segments, there are 24 base members.) Thesupport element 448 is essentially a flat planar element having fouredges (sides)—a top edge for supporting the expanding segment 328, afirst side edge which rides in the groove 442 a of a given groove pair,and a second side edge which rides in the groove 442 b of the givengroove pair. The support element 448 also has a bottom edge, but theshape of that edge is of no particular importance (as contrasted withthe bottom edge ramp surface of the ramp element 348). Preferably, thesupport element 448 is separate from the expanding segment 428, but itis within the scope of the invention that it is integrally formedtherewith. In the case that the support element 448 is not formedintegrally with the expanding segment 428, the expanding segment 428 maybe attached in any suitable manner to the support element 448.

Two guide rings (hubs) 458 a and 458 b (collectively referred to as“458”) are disposed at axially spaced apart positions on the spindle (oneither side of the centerplane). The guide rings 458 are suitably in theform of generally planar discs (rings, since they are discs with a holein the middle) which are centered on the axis 404, and are parallel withone another. The guide rings 458 are not fixed to the spindle. Rather,although they may be keyed (or splined) to the spindle so that they willrotate with the spindle, they are free to move axially along thespindle, towards and apart form one another, from a minimum distance(essentially touching one another), to a maximum distance from oneanother, remaining parallel with each other irrespective of the axialdistance form one another.

An overlapping linkage mechanism 460 is provided between the guide rings458 and the support element 448. The linkage mechanism comprises:

a first elongate link 462 having an end pivotally attached to a one (458a; left, as viewed) of the guide rings 458, and an opposite endpivotally attached adjacent (near) a one (right, as viewed) end of thesupport element 448; and

a second elongate link 464 having an end pivotally attached to the other(458 b; right, as viewed) of the guide rings 458, and an opposite endpivotally attached adjacent (near) an opposite (left, as viewed) end ofthe support element 448.

The links 462 and 464 overlap each other (cross over one another), butare not pivotally attached to each other, as would be the case with a“scissors” type linkage, nor are they parallel to each other, as wouldbe the case with a two-link “toggle” type linkage.

In FIG. 4A (compare FIG. 3B) the center section 420 is shown in itscollapsed (or “fully-collapsed”) position. In this position, the guiderings 458 are spread far apart from one another (essentially as farapart as they are capable of spreading), and the support element 448and, consequently, the expanding segment 428 is at its minimal radialdistance from the axis 404. In other words, the diameter of the centersection 420 is at a minimum in this collapsed position. In thiscollapsed position, the outer surface of the center section 420 hassubstantially the same diameter as that of the outer surfaces (306) ofadjacent end sections (322, 324). In this collapsed position, the innerliner of a tire carcass may be applied.

In FIG. 4B (compare FIG. 3D), the center section 420 is shown in itsfully-expanded position. In this position, the guide rings 458 are closetogether (e.g., essentially zero distance apart from one another), andthe support element 448 and, consequently, the expanding segment 428 isat its greatest greater radial distance from the axis 404. In otherwords, the center section 420 is now fully-expanded. In thisfully-expanded position, the outer surface of the center section 420 hasa much greater diameter than that of the outer surfaces (306) ofadjacent end sections (e.g., 222, 224). Concurrently with the drum inthe fully-expanded position, separately actuated bead locks (not shown)cause the beads to be firmly set. Next, the ends of the carcass can thenbe turned up, in a final step of carcass construction. Then, the centersection 420 of the drum can be partially collapsed (e.g., returned to asemi-expanded position), the bead locks collapsed and the carcass can beremoved for further processing, such as the application of a treadpackage in a second stage tire building machine.

In the collapsed condition (FIG. 4A), the links 462 and 464 are bothnearly parallel to the axis 404. For example, at an angle of 19.6degrees with respect thereto. In the expanded condition (FIG. 4B), thelinks 462 and 464 are at an angle approximately halfway between parallelto and perpendicular to the axis 303, such as at an angle of 46.2degrees with respect thereto. This provides for a relatively compactmechanism with a good operating range.

Although not shown, the center section can be expanded to any diameterbetween collapsed and fully-expanded, as determined by the spacing ofthe guide rings 458 from one another. For example, in a semi-expandedposition, the ply of a tire carcass may be applied. It is preferred thatthe two guide rings 458 remain equidistant from the centerplane of thecenter section 420 of the drum while they are moving in their range ofpositions. In this manner, forces are evenly (symmetrically) distributedalong the length (L_(C)) of the support element 448 and the expandingsegment 428.

In this example, with the overlapping linkage, the relationship betweenguide ring spacing and center section diameter is inverse—the closer theguide rings are to one another, the greater the diameter of the centersection. In the previous example (wedge/ramp), the relationship betweenguide rings spacing and center section diameter is direct—the closer theguide rings are to one another, the lesser the diameter of the centersection. In either case however, the diameter of the center section 320and 420 is proportional (directly or inversely, respectively) to thespacing between the wedge elements 358 or guide rings 458, respectively.

The overlapping linkage mechanism of FIGS. 4A–4C is superior to a togglelinkage, for example as shown in the aforementioned U.S. Pat. No.4,929,298 with regard to being able to apply forces to the expandingsegment in a manner which is symmetrical about the centerplane,throughout the range of expansion for the drum. A toggle linkage,wherein two links move in unison parallel to one another, is inherentlynot symmetrical about the centerplane. This symmetry, as in the previous(wedge) embodiment, can be of profound significance in achievinguniformity in the layup of the tire carcass.

The overlapping linkage embodiment of FIGS. 4A–4C is similar to thewedge/ramp embodiment of FIGS. 3A–3D, in the following regards:

-   -   both are for expanding and collapsing a center section (220,        320, 420) of a tire building drum;    -   both act upon expanding segments (228, 328, 428) of the center        section;    -   both do not act upon the fixed segments (226, 326, 426) of the        center section;    -   both employ flanges (340, 440) which have grooves (342, 442) for        guiding a ramp element (348) or support element (448) which        supports the expanding segment (328, 428);    -   both have elements (358, 458) which move axially to effect the        expansion/collapse of the center section;    -   both exert expanding forces on the expanding segments in a        manner which is symmetrical about the centerplane.

The symmetry of forces exerted (urged) upon the expanding segments,about the centerplane, is non-trivial. As mentioned above, a carcass plywhich is lopsided (longer cords on one side of the tire than the otherside) can cause a variety of tire nonuniformity problems includingstatic imbalance and radial force variations. The present inventionaddresses one potential source of such nonuniformities—namely, imprecise(e.g., non-cylindrical) expansion of the drum.

In both embodiments, when the center section (320, 420) is collapsed,the surface of the drum is substantially continuous, smooth,uninterrupted (flat), and this is advantageous for innerlinerapplication. It is within the scope of the invention that means forproviding a vacuum, through selected ones of the segments (either fixedor expanding), to the surface of the drum, to hold the innerlinersecurely thereon, be provided, in any suitable manner. When the centersection is semi-expanded, the surface is also substantially flat, suchas would be advantageous for ply application. Both embodiments can use aroller screw system for center section expansion. The mechanism formoving the wedges 358 or guide rings 458 depends largely on otherfactors present in the overall drum construction, and can be adapted ona case-by-case basis.

The overlapping linkage embodiment of FIGS. 4A–4C is different from thewedge/ramp embodiment of FIGS. 3A–3D, in the following regards:

-   -   in the wedge/ramp embodiment, rubber bands (338) are used to        collapse the center section (320);    -   in the overlapping linkage embodiment, the links (462, 464)        themselves effect collapse of the center section;    -   in the wedge/ramp embodiment, the center section (320) expands        when the wedges (358) move axially apart, and retracts when the        wedges (358) move together.    -   in the overlapping linkage embodiment, the center section (420)        expands when the guide rings (458) move closer together, and        retracts when the guide rings (358) move farther apart.

The overlapping linkage design tends to provide more expansion range ina narrower width (L_(C)), allowing the minimum drum width to shrink, forexample from 250 mm (for the wedge embodiment) to 200 mm (for thelinkage embodiment) .

Some exemplary dimensions for the center section (420 of the linkageembodiment are presented in the following table.

Tire Size (in.) 14 15 16 17 18 19 20 Rim Dia (in.) 14 15 16 17.2 18.219.2 20.2 Expanded (mm) 391 416 441 472 497 523 548 Intermediate (mm)338 364 390 420 444 468 493 Collapsed (mm) 308 334 350 380 404 428 453expansion (mm) 83 82 91 92 93 95 95

FIG. 4D illustrates an alternate embodiment of a support element 448′which is provided with two holes 442 a and 442 b (compare 342 a and 342b) for receiving biasing members comparable to the biasing members 338shown in FIGS. 3A–3D. The biasing members, suitably in the form ofrubber bands, would exert a “collapsing” radial force on the supportelement 448′.

Extended Mobility Tires

FIG. 5 is a partial cross-sectional view of an exemplary tire carcass asit is laid up on a tire building drum, according to the invention. Anend of an expanding segment 528 is shown. First, First, a center sleeve502 is installed on the surface of the drum and extends over theexpanding segment 528. . An upper turnup bladder 503 and a lower turnupbladder 505 extends beyond the drum. The tire carcass comprises thefollowing major components, in the following order:

-   -   an innerliner 504;    -   a first sidewall insert (pillar) 506;    -   a first ply (ply 1) 508;    -   a second sidewall insert (post) 510;    -   a second ply (ply 2) 512;    -   a bead 514;    -   an apex 516;    -   a chafer 518; and    -   a sidewall 520.

Other components, such as chipper, gum toeguard and fabric toeguard maybe added to the carcass, as may be desired, but form no special part ofthe present invention.

Although the invention has been illustrated and described in detail inthe drawings and foregoing description, the same is to be considered asillustrative and not restrictive in character—it being understood thatonly preferred embodiments have been shown and described, and that allchanges and modifications that come within the spirit of the inventionare desired to be protected. Undoubtedly, many other “variations” on the“themes” set forth hereinabove will occur to one having ordinary skillin the art to which the present invention most nearly pertains, and suchvariations are intended to be within the scope of the invention, asdisclosed herein.

1. A tire building drum having an axis and a centerplane intersectingthe axis, comprising: a plurality of axially extending,circumferentially spaced-apart expanding segments, each of saidexpanding segments being expandable from a first radius in a collapsedcondition of said drum to a second radius in an expanded condition ofsaid drum; a pair of flanges centered about the axis at a fixed distancefrom one another; a plurality of ramp elements, each supporting anexpanding segment, disposed between the flanges and radially guidedbetween the flanges; two conical elements, each disposed coaxiallybetween the pair of flanges, axially moveable therebetween, and having atapered face; wherein the tapered face of each of the two conicalelements engages an inner surface of the ramp elements for forcing theexpanding segments radially outward from the axis; characterized inthat: there are two conical elements, each frustoconical disposedcoaxially with their bases facing each other; and the inner surfaces ofthe ramp elements are V-shaped; and a plurality of base memberssupporting a plurality of fixed segments; in each flange, a firstplurality of grooves for receiving opposite side edges of the pluralityof base members.
 2. Tire building drum, according to claim 1, whereinwhen the conical elements move farther apart from one another, they urgethe ramp elements radially outward from the axis.
 3. Tire building drum,according to claim 1, further comprising: in each flange, a secondplurality of grooves disposed on an inner surface thereof and extendingradially from the axis, for radially guiding the plurality of rampelements.
 4. Tire building drum, according to claim 1, wherein: theexpanding segments, ramp elements, flange and conical elements are alllocated in a center section of the drum.
 5. Tire building drum,according to claim 1, wherein: both of the two conical elements exerts aforce on each of the ramp elements.
 6. Tire building drum, according toclaim 5, wherein: the forces exerted by each of the two conical elementsare symmetrical about the centerplane.
 7. Tire building drum, accordingto claim 1, further comprising: a plurality of fixed segments disposedbetween the plurality of expanding segments.
 8. Tire building drum,according to claim 1, wherein: end portions of the expanding segmentsare contoured to have pockets for receiving components of a tire carcassbeing laid up on the drum.
 9. Tire building drum, according to claim 1,further comprising: biasing members exerting a collapsing radial forceon the ramp elements.
 10. A tire building drum having an axis and acenterplane intersecting the axis, comprising: a plurality of axiallyextending, circumferentially spaced-apart expanding segments, each ofsaid expanding segments being expandable from a first radius in acollapsed condition of said drum to a second radius in an expandedcondition of said drum; a pair of flanges centered about the axis at afixed distance from one another; a plurality of ramp elements, eachsupporting an expanding segment, disposed between the flanges andradially guided between the flanges; two conical elements, each disposedcoaxially between the pair of flanges, axially moveable therebetween,and having a tapered face; wherein the tapered face of each of the twoconical elements engages an inner surface of the ramp elements forforcing the expanding segments radially outward from the axis;characterized in that: there are two conical elements, eachfrustoconical disposed coaxially with their bases facing each other; theinner surfaces of the ramp elements are V-shaped; a plurality of basemembers supporting a plurality of fixed segments; in each flange, afirst plurality of grooves for receiving opposite side edges of theplurality of base members; and the conical elements have notches atcircumferential positions about the outer surface of their respectivebases for receiving a bottom edge of the base members.